The recently remarkable development in extensively various machines including semiconductor fabricating equipment and so on has needed linear motion guide units that are expected to get any parts moving in a reciprocating manner with precise position control and smooth movement, despite being made reduced in construction. Meanwhile, modern linear motion guide units have been especially required to meet with the maintenance-free operation regarding lubrication for rolling elements from many aspects of conserving energy as well as keeping running cost and maintenance cost of equipment reasonable. A diversity of machines including semiconductor fabricating equipment, assembly machines, inspection instruments and so on, nevertheless, is looking to the linear motion guide unit that could ensure the maintenance-free operation more securely than even when used under high-speed, high-cyclic operating condition.
In the commonly assigned Japanese Patent Laid-Open No. 2001-82469, there is disclosed a linear motion guide unit in which a return passage in a slider is made of sintered resinous member of cellular or porous structure that is impregnated with lubricant to ensure lubrication for the rolling elements over a long-lasting operation, improving the duration of maintenance-free condition.
The prior linear motion guide unit constructed as stated earlier is comprised of an elongated guide rail and a slider movable lengthwise relative to the guide rail by virtue of more than one rolling element that is allowed rolling into the load-carrying race from the non-loaded return passage cut in the slider, and vice versa in a circulating manner. The return passage is constituted with a sleeve of sintered resinous member having cellular structure, which fits into a fore-and-aft hole made in the slider so as to allow the rolling elements running inside the sleeve. Lubricant soaked into the cellular texture of the sintered resinous member is reserved or held in the cells or pores in the cellular structure. Oily ingredient of the lubricant is constantly applied on the rolling elements for long-lasting operation while they roll through inside the sleeve, and oil films around any rolling elements get lubricating smoothly the load-carrying surfaces as the rolling elements run through load race, with accompanying reduced frictional resistance against the slider, thereby improving the durability of the linear motion guide unit.
However, it still remains a further challenge to the prior linear motion guide unit as recited earlier to continue supplying any additional lubricant to the rolling elements.
A linear guideway with self-lubrication system is moreover disclosed in Japanese Utility Model Registration No. 3066116, in which the rolling elements are directly lubricated with grease while they roll through the non-loaded return passage. The prior guideway as stated earlier is expected to conserve grease as well as keep the environment against pollution caused by massive leakage of grease. Besides, grease after run out would be replenished without disassembly of the self-lubrication system. The prior linear guideway with self-lubrication system includes an oil reservoir to store grease inside the slider, a grease path to lead grease out of the oil reservoir into the non-loaded return passage, a sealing pad to keep grease against leakage, and a fibrous textile packed in the oil reservoir to ooze slowly the non-loaded return passage with grease on the principle of siphonage. The linear guideway receives further lubrication with any lubricator when its grease runs out.
With the linear guideway with self-lubrication system reserving only as much lubricant as once needed, nevertheless, the reserved quantity of lubricant might be not necessarily enough to ensure the maintenance-free operation, while how quantity of lubricant is replenished gets unknown easily. Moreover, the lubricant applicators are much tough to select and use them.
Another linear guideway is disclosed in US2003/0164264A1, in which a lubricating structure sits transversely inside a slider and mainly contains an oil reservoir inside the slider. The oil reservoir extends along both sides of the slider to communicate with slide way. A diversion device of fibrous material such as felt and the like is installed in the oil reservoir. A sealing member is installed correspondingly to the oil reservoir on one end of the slider. The diversion device at one end thereof reaches a guideway cut in the slider.
The prior linear guideway with the lubricating structure as stated earlier is highly tough to work it because a groove to fit over the diversion device has to be cut in the slider.
A further another linear motion guide unit with lubricating means is disclosed in Japanese Patent Laid-Open No. H09-303392, in which a lubricating member made of rubber or synthetic resin containing lubricant is built in a slider to make automatic application of lubricant to the rolling elements inside the slider with no necessity of replenishing lubricant from the outside of the slider. The slider is made therein with a lubrication port where the lubricating member is installed and biased inwards by resilient force to get the lubricant oozing out of the lubricating member to reach a circulating passage where the rolling elements roll through there.
With the prior linear motion guide unit with lubricating means constructed as stated earlier, constant application with certainty of lubricant to the return passage couldn't be expected because the quantity of lubricant oozy out of the lubricating member depends on the temperature rise or the biasing force exerted by the resilient plug. The linear motion guide unit of the type recited in the last-mentioned prior art, moreover, would be unsuitable for steady application of lubricant to every location to be lubricated because the lubricant is left to flow in gravitational direction.
There, advanced technology has come to hope any linear motion guide unit that can be expected to increase the volumetric quantity of lubricant prepared for the application to the return passage, making certain of maintenance-free operation for the long-last service life and also make the replenishment of lubricant easier by employment of a replaceable cartridge system.